U0133 Lost Communication With Active Roll Control Module (ARCM)
OBD2 Error Codes

U0133 Lost Communication With Active Roll Control Module (ARCM)

U0133 Lost Communication With Active Roll Control Module (ARCM)

OBD-II DTC Datasheet

Lost Communication With Active Roll Control Module

What does this mean?

This is a generic communication system diagnostic trouble code that applies to most makes and models of vehicles.

This code means that the Active Roll Control Module (ARCM) and other control modules on the vehicle are not communicating with each other. The circuitry most commonly used for communication is known as Controller Area Bus communication, or simply the CAN bus.

Without this CAN bus, control modules cannot communicate and your scan tool may not receive information from the vehicle, depending on which circuit is involved.

ARCM receives input from various sensors, some of which are directly connected to it, and some are transmitted over a bus communication system. These inputs allow the module to control the vehicle when a rollover seems possible. When the main brakes are applied, it prevents the vehicle from overturning by alternately applying the brakes at different corners of the vehicle. Typically, this system is used on SUVs and light and medium-duty trucks, but can be used if the manufacturer sees fit for other alternative applications.

Troubleshooting steps may vary depending on the manufacturer, the type of communication system, the number of wires, and the colors of the wires in the communication system.

Severity and symptoms

The severity in this case depends on the system. Because the suspension system provides safety during violent steering and braking maneuvers, safety is a concern when diagnosing these systems. In addition, safety is important when servicing these systems. ALWAYS refer to the service information before disassembling / diagnosing these systems.

Symptoms of a U0133 engine code may include:

  • Fault indicator light is on
  • Suspension warning lamp is on
  • The traction control indicator light is on or flashing, depending on the system

reasons

Usually the reason for installing this code is:

  • Open in CAN + bus circuit
  • CAN bus break - electrical circuit
  • Short circuit to power in any CAN bus circuit
  • Short to ground in any CAN bus circuit
  • A power or ground failure to the ARCM module is the most common
  • Rarely - the control module is faulty

Diagnostic and repair procedures

A good starting point is always to check the Technical Service Bulletins (TSB) for your particular vehicle. Your problem may be a known issue with a known manufacturer-released fix and could save you time and money while troubleshooting.

If your scan tool can access trouble codes and the only code you are retrieving from other modules is U0133, try accessing the Active Roll Control Module (ARCM). If you can access codes from the ARCM, then the U0133 code is either intermittent or a memory code. If you cannot access codes for the ARCM, then the U0133 code that the other modules are setting is active and the problem already exists.

The most common fault is loss of power or ground to the ARCM module.

Check all fuses supplying the ARCM on this vehicle. Check all grounds for the ARCM. Locate grounding attachment points on the vehicle and make sure these connections are clean and secure. If necessary, remove them, take a small wire bristle brush and baking soda / water solution and clean each one, both the connector and the place where it connects.

If any repairs have been made, clear the DTCs from memory and see if U0133 returns or you can contact the ARCM. If no code is returned or communication is restored, the problem is most likely a fuse / connection issue.

If the code returns, look for the CAN C bus connections on your specific vehicle, especially the ARCM connector. Disconnect the negative battery cable before disconnecting the connector on the ARCM control module. Once detected, visually inspect the connectors and wiring. Look for scratches, scuffs, exposed wires, burn marks, or molten plastic. Disconnect the connectors and carefully inspect the terminals (metal parts) inside the connectors. See if they look burnt or have a green tint indicating corrosion. If you need to clean the terminals, use an electrical contact cleaner and a plastic bristle brush. Allow to dry and apply electrical grease where the terminals touch.

Before connecting the connectors back to the ARCM, perform these few voltage checks. You will need access to a digital volt ohm meter (DVOM). Make sure you have power and ground at the ARCM. Access the wiring diagram and determine where the main power and ground sources enter the ARCM. Reconnect the battery before continuing, with the ARCM still disconnected. Connect the red lead from your volt meter to each B+ (battery voltage) source entering the ARCM connector, and the black lead from your volt meter to a good ground (if unsure, the negative battery terminal always works). You should see a battery voltage reading. Make sure you have a good ground. Connect the red lead from your volt meter to the battery positive (B+) and the black lead to each ground circuit. Once again, you should see battery voltage with each connection. If not, troubleshoot the power or ground circuit.

Next, check the two communication circuits. Find the CAN C+ (or HSCAN+) circuit and the CAN C- (or HSCAN – circuit). With the black lead of the voltmeter connected to a good ground, connect the red lead to CAN C+. With the key on and the engine off, you should see about 2.6 volts with a little oscillation. Then connect the red lead of the voltmeter to the CAN C- circuit. You should see about 2.4 volts with a little oscillation. Other manufacturers show CAN C- at about 5 volts and a oscillating key with the engine off. Check your manufacturer's specifications.

If all tests pass and communication is still not possible, or you were unable to clear the U0133 trouble code, the only thing to do is to seek help from a trained automotive diagnostician, as this would indicate a faulty ARCM. Most of these ARCMs need to be programmed or calibrated for the vehicle in order to be installed correctly.

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